Want big tube room filling sound without the trouble or expense of big tube equipment? Look no further! This 9 tube amp is simple to operate, powerful, and uses only 3 types of tubes. This amp features a 6BQ5 push-pull output for each channel, and two quiet, reliable 6EU7 tubes in each channel as well. A 5U4-G keeps plenty of power flowing. You have complete control with powerful bass and treble tone controls, and a balance control compensates for any speaker/room or source audio deficiencies.
The Magnavox-style output section uses a paraphase inverter and a minimum of circuit components. An inverse feedback loop minimizes distortion to give you clean, room filling tube sound. This is a powerful amplifier, if you live in a dorm room or small apartment, you may have difficulty, as this amplifier does not like to play at low volume levels.
| Control Resistors | ||
| Resistor ID | Value (ohms) | Function, Notes |
| R1A & B | Dual-section 500K audio taper 1/2W | Volume Control |
| R2A & B | Dual-section 1M linear taper 1/2W | Bass Control |
| R3A & B | Dual-section 1M linear taper 1/2W | Treble Control |
| R4 | 750 linear taper 1W | Balance Control |
| Fixed Resistors | ||
| R5, R23 | 2.2K 1/2W | Input amp cathode |
| R6, R24 | 220K 1/2W | Input plate load |
| R7, R25 | 10K 1/2W | Bass tone comp |
| R8, R26 | 100K 1/2W | Bass tone comp |
| R9, R27 | 100K 1/2W | Audio coupling |
| R10, R28 | 2.7K 1/2W | Tone amp cathode |
| R11, R29 | 82K 1/2W | Tone amp plate load |
| R12. R30 | 470K 1/2W | Grid load |
| R13, R31 | 47K 1/2W | Grid input |
| R14, R32 | 5.6K 1/2W | Inverter cathode |
| R15, R33 | 2.2K 1/2W | Driver cathode |
| R16, R34 | 220K 1/2W | Plate load |
| R17, R35 | 220K 1/2W | Plate load |
| R18, R36 | 220K 1/2W | Output grid |
| R19, R37 | 39K 1/2W | Inverter grid |
| R20, R38 | 470K 1/2W | Output grid |
| R21, R39 | 220K 1/2W | Monitor isolation |
| R22, R40 | 3.9K 1/2W | Feedback coupling |
| Power Resistors | ||
| R41 | 100 10W wire wound | Output cathodes |
| R42 | 10K 5W wire wound | Voltage divider |
| R43 | 15K 2W metal oxide | Voltage Divider |
| R44 | 750 5W wire wound potentiometer | Hum adjust |
| Fixed Capacitors | ||
| Capacitor ID | Value | Function, Notes |
| C1, C10 | 0.047mF 630V | Audio coupling |
| C2, C11 | 0.002mF 630V | Bass tone comp |
| C3, C12 | 0.02mF 630V | Bass tone comp |
| C4, C13 | 0.0002mF 630V | Treble tone comp |
| C5, C14 | 0.002mF 630V | Treble tone comp |
| C6, C15 | 0.047mF 630V | Audio coupling |
| C7, C16 | 100mmf 630V | B+ decoupling/snubber |
| C8, C17 | 0.0047mF 630V | Audio coupling |
| C9, C18 | 0.047mF 630V | Audio coupling |
| C19 | 0.01mF 1400V | Line bypass |
| Electrolytic Capacitors | ||
| C20 | 22mF 25V | Cathode bypass |
| C21 | 47mF 450V | Filter |
| C22 | 33mF 450V | Filter |
| C23 | 10mF 450V | Filter |
| C24 | 33mF 450V | Filter |
| Choke ID | Inductance (henries @ 1000 cps) | Current, notes |
| L1 | 1 henry | 130 ma @ 330 volts, U-bracket |
| Power Transformer, T1 | |||
| Primary | Sec. 1 | Sec. 2 | Sec.3 |
| 117V AC 60cps .92A | 600V CT 130ma | 5 volts 3 amps | 6.3 volts 4 amps |
| Output Transformers T2, T3 | |
| Primary Impedance | Secondary Impedance |
| 8000 ohms,CT @ 400 cps | Matched to speakers, with a tap @ 4 ohms for feedback. |
| Miscellaneous Parts | ||
| Part ID | Description | Function, Notes |
| SW1A & B | 2-pole, 6-throw make-before break switch | Audio Selector Switch |
| SW2 | Single-pole, single-throw switch, 5A rated | Power Switch |
| V1 | 6EU7 | Input amp-tone amp left channel |
| V2 | 6EU7 | Driver-phase inverter left channel |
| V3 | 6EU7 | Input amp-tone amp right channel |
| V4 | 6EU7 | Driver-phase inverter right channel |
| V5 | 6BQ5 | Output left channel |
| V6 | 6BQ5 | Output left channel |
| V7 | 6BQ5 | Output right channel |
| V8 | 6BQ5 | Output right channel |
| V9 | 5U5-G | Current rectifier |
Created 11-21-09
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